The present invention relates to signal translating devices and to methods of programming such devices to provide a given type of output signal. The invention is particularly useful in transversal filters of the SAW (surface acoustic wave) type which are programmable to provide a given impulse-response function, and is therefore described below with respect to this application.
A transversal filter of the SAW type includes an acoustic charge transport body, e.g., of piezoelectric material, for transporting a surface acoustic wave along the length of the body. A plurality of electrical conductors spaced along the length of the body define a plurality of code sections for generating, from the SAW (surface acoustic wave), phase-coded electrical signals which are outputted via a plurality of taps spaced along the length of the device. Such transversal filters can be designed to provide any desired impulse-response function.
Generally, such transversal filters are designed at the time of production for the specific impulse-response function to be provided by the filter. This increases the costs for manufacturing, marketing, and inventoring such filters. A number of programmable transversal filters have been described in the literature permitting the user to program the filter according to the desired impulse-response function; see for example, in U.S. Pat. Nos. 4,665,374 and 5,225,798. However, insofar as we are aware, the programmable transversal filters heretofore proposed have not found widespread use.